Recent work suggests that significant differences might exist in the microwave absorption spectra of normal and malignant cells. In addition, there is other evidence that microwave resonance radiation might be used in cancer therapy. Experiments are in progress to determine the absorption spectra in the 26.5-90 GHz rang of: (a) Biological compounds (water, proteins, DNA, RNA, etc.); (b) biological solutions (MEM, saline, Luria broth, etc.); (c) cell suspensions (red blood cells, bacteria, yeast, fungi, viral suspensions, normal and transformed mammalian cells, etc.). The mammalian cell studies include: (a) B16 murine melanoma and transformed BHK 21/C13 cells; (b) two lines of normal and transformed cells bearing temperature-sensitive viruses; (c) three different systems in which normal cells can be compared with: virus transformed cells, isolated spontaneous transformants and drug-induced transformants. Evaluation of the quantitative results obtained from these experiments will show whether diagnostic microwave spectroscopy can be used as a tool in cancer screening. Experiments are also being conducted to determine whether significant differences in sensitivity to microwave irradiation exist between normal and transformed cells. These studies are being carried out using a novel procedure recently developed in this laboratory which allows us to directly irradiate cells in culture without local heating. The experiments include a study of the effect of microwave irradiation on: (a) Cell growth; (b) morphology of several cloned cell lines and primary cell cultures using both light and electron microscopy; (c) analysis of biochemical parameters such as RNA and protein synthesis. These studies will indicate the extent to which frequency-specific athermal microwave irradiation can be used as a possible form of cancer therapy.